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Enormous Influence of El-Nino Phenomenon on Fluctuation of Weather and Climate of the Entire Planet.

Semenov E.K.



El Nino, in the Spanish language, means young one. This is the name of abnormal warming of the surface waters of the Pacific along the shores of Ecuador and Peru, which occurs once every several years. This affectionate name reflects the fact that the beginning of El Nino occurs most often during Christmas holidays (the end of December). The fishermen from the West Coast of South America connect this weather phenomenon with the baby Jesus.

During normal years, the entire coastline of the Pacific along South America--between Talara and Kalya--the average temperature of the oceans surface vacillates between 15-16 o C and 18-19 o C according to the season. This is due to the rise of cold deep water (upwelling) caused by the cold surface Gumboldt (Peruvian) stream. The biological effect of upwelling is tremendous. Water comes up from the depth of 100-300 m from the strata with large amounts of nitrogen and phosphorus--elements that are necessary for the development of phytoplankton, helping to increase the amounts of zooplankton and consequently increase the amount of food available for fish. Of all bodies of water, this coastline alone--a comparatively small and insignificant fraction of all global waters--accounts for 22% of the worlds fish-catch.

During the period of El-Nino the average temperature of the ocean surface in the coastal zone of Ecuador and Peru increases to 21-23 o C, and occasionally to 25-29 oC. The sharp increase in the waters temperature near the oceans surface is responsible for the disappearance of numerous marketable fish, as well as a decrease in the number of sea dwelling birds who feed on these fish and who are unaccustomed to this unusual and unfortunate weather.

The increase in the average water temperature at the coast of South America is related to a change of the overall ecosystem and ocean atmosphere, as well as to the appearance of other not less remarkable anomalies in the atmosphere.

Collected data testifies to the regularity of the appearance of El-Nino with an interval of 4-12 years, and, on average, with a 6-7 year interval. The duration of El-Nino itself ranged from 6-8 months to 3 years, with a most common duration of 1-1.5 years. This considerable range in duration results in the difficulty of accurately forecasting weather phenomenon.

Beginning in the 1980s, the characteristics of ocean and atmosphere changes have changed considerably. Wide scale warming of the equatorial Pacific now began occurring in central regions in the middle of the calendar year in the area of time zone change (180) and afterwards spread to the East, attaining its maximum increase in the end of the year and decreasing again a few months later. This was accompanied by the growth of atmospheric pressure above Indonesia and a changing of the equatorial location in the central regions of the Pacific. The anomaly of the equatorial west wind which was caused by this particular change of bar poles promoted the pushing up of warm water to the coast of South America and deepening the thermo-wedge--the boundary between the displaced warm surface layer and deeper cold waters.

The repetition of the cold phases of the cycle (La-Nina) became much less frequent. Now these cold periods dont accompany every El-Nino: the average temperature either returns to normal, or remains above the average. From the middle of 1970s the equatorial Pacific could have been regarded as a warming thermostat. To determine the cause of the changes in the character of El-Nio is rather difficult, as its nature has not been studied conclusively as of yet. A number of authors, for example, consider that the weakening of the cold phase is connected with the growth of an average global tropospheric temperature, which in 1924 became as high as 0.31 o C above the average temperature for the period of 1951-1980. This warming began in the end of 1970s. Other scientists feel that, on the contrary, an increase of the average temperature of the Pacific surface water is the cause for the global warming of the last two decades.

The last El-Nio, which began to gain its strength in December 1996 and ended only in 1998, can become known as a century phenomenon.

According to the estimates of a British meteorological division, the overall monetary loss due to El Nio can be estimated in excess of $50 billion. Four hundred fifty experts from 27 countries affected by the disaster gathered at the inter-government meeting at Guayakil (Ecuador) from the 9th-13th of November, 1998. These experts sadly concluded that up to 26,700 people died; 541 thousand people suffered through diseases (mainly cholera and malaria), 117 million were wounded and suffered from malnutrition. Direct losses alone have been estimated at $14 billion and their socio-economic consequences necessitated $20-30 billion more.

El-Nino never appeared as often as it has in the last decade. It furthermore



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